The goal of this proposal is to test the hypothesis that nonlinguistic auditory perception is essential for normal speech development. Despite the evidence that children with developmental language disorders (DLD) have deficits in processing low-level acoustic information, the specific nature of the auditory perceptual deficits is not known. The proposal will investigate the ability to segment or group acoustic input because impairments in the ability to organize sound could contribute to poor speech discrimination skills and interfere with learning in common multi-source listening situations, such as the classroom. The ultimate purpose is to ascertain standard measures of the normal development of perceptual sound organization in school-aged children upon which measures in language-impaired children can be compared. School-aged children (6-11 years) and young adults (21-40 years) will be studied. A combination of electrophysiological and behavioral measures will be examined. We will analyze selected components of event-related brain potentials (ERPs) that index different stages and attentional states of auditory processing. ERP analysis will be supplemented by analysis of frequency-specific components in the electroencephalogram (EEG). This approach will enable us to assess developmental features of how cortical sensory representations of sound impact upon perception of multiple sound streams. Assessing the relationship between stimulus-driven and attention-driven processes in typically language developing (TLD) children (via the studies proposed in the current application) is crucial for designing future studies that test whether or not language impairments can be attributed to stimulus-driven cortical sound representations, and to assess the degree to which attentional factors influence perception of sound streams. We will test the following hypotheses: 1) Stimulus parameters determining the segregation of sounds change as a function of age. 2) Electrophysiological indices of stream segregation correlate with behavioral measures in TLD children and adults. 3) Perceptual training facilitates stream segregation, as indexed by changes in electrophysiological and behavioral measures. The use of the ERP and EEG measures to assess developmental markers of sound organization is advantageous because these indices can be obtained in young children and impaired populations. This methodological approach has the potential to be an important non-invasive tool for diagnosis and assessment of central auditory processing deficits that lead to impaired language. [unreadable] [unreadable]